I think points per level is a function of the time spent for the goldberg machine to work. Like, if you complete the thing in 3 seconds, you'll get 3 points. But when I did a super long loop on level 21 I got 29 points.
For levels 9 and 10. the only combinations I can see working would be big splash + slow, massive teleport, or machine gun. The all pure gems strategy does not seem to deal enough damage to win. :/.